Communication between MFC ocx and a thread

Situation :
I've created an ocx in MFC. In one of its method, I need to create a thread.
The main thread of the ocx, continues processing after creating this working thread. This working thread receives during its creation a pointer to the ocx so it can use its public member functions.

Problem :
The main thread must be able to process messages send by the worker thread (now done by SendMessage). Once the main thread receives such a message, it'll call its private Event dispatching method.
I don't succeed in sending a message from the worker thread to the main thread.
The method 'SendMessage' hangs, I try to send a message to a hidden window created by the main thread.
How should this be handeld.
Thanks for any advice.
jlsjls

'This working thread receives during its creation a pointer to the ocx so it can use its public member functions.'
That might not be a good idea. Use messages to initiate processing and return results via event/memory protected by CCriticalSection or other mechanism.

'The main thread must be able to process messages send by the worker thread (now done by SendMessage). '
SendMessage could cause a blockage (each thread waiting for the other to respond before continuing), PostMessage would be more advisable.
Does your thread have a HWND for the OCX to pass the messages to. (Using CWnd pointers and the like is dangerous between threads).

The reason why the worker thread uses 'SendMessage' is that it needs to wait till the ocx (application) has handled the event. The worker thread sends a message to a hidden window in the ocx. The window procedure should handle this message and fire an event to the application. The application needs to (based on parameters of the event) set some values in this event. When finished, the worker thread can process the results.

You could use logic like
PostMessage(....)
WaitForEvent(...)
as you are firing an event back to signal the thread to continue.

Back to your original question.
Are you passing the HWND of this hidden window to the thread. pWnd->GetSafeHwnd() will get the HWND of a CWnd* object. If you aren't using the HWND then that could be why the SendMessage isn't getting to the hidden window.

Yes, I'm passing the HWND of the hidden window to the thread. I set it as a public member on my ocx and a pointer to this ocx is passed in the creation of the worker thread.
When debugging my worker thread, I can see the value of the HWND and it's the same as the one I noticed by using Spy++ (where I see the handle of the hidden window).
Maybe I don't need to create the hidden window, you refer to 'pWnd->GetSafeHwnd()' ; how can I retrieve that from an ocx.
I've created a hidden window by the method 'CreateWindow'. This returns a handle to a window which I'm using in my worker thread.
I need to leave the office now, so I won't immediately respond to your answer.
... I'll be back...

When I'm debugging, I don't receive the message in the message handler of the hidden window.
I've already added logging in this message handler.
I'm not sure if my message handler is correct?? Should I use some windows dispatching (thread with GetMessage() ; DispatchMessage()?? How should this be done?

My error; the reason why the main thread wasn't responding is due to the fact that :
I've added the call WaitForSingleObject(...,INFINITE) and waited for an event which
wasn't fired by the worker thread.
AndyAinscow thanks anyhow for your effort to help me.

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